2014 Outstanding Repair & Rehabilitation Project The 606- | Viaduct Repairs

By Kevin Doyle

ocated on the northwest side of , Trail. “The 606” gets its name from the zip code IL, the abandoned railway known as the prefix, 606, which all Chicagoans share; the LBloomingdale Line, originally constructed in Bloomingdale Trail is named for the street right- 1873, runs east and west through four dense of-way where the trail is located. The proposal neighborhoods including Bucktown, Logan encompassed structural concrete repair and rehab­ Square, Wicker Park, and Humboldt Park. The ilitation work of 36 concrete bridges and retaining line starts at the Kennedy expressway, just north walls, landscaping, bridge deck waterproofing, of the loop, half way between Wrigley Field and new bridge construction, decorative guardrail, new US Cellular Field, and heads west for 2.67 miles lighting and security cameras, the creation of new (4.29 km). The line was built shortly after the parks, and installation of numerous access ramps Chicago fire in 1871 by Chicago and Pacific along the length of the trail. Railroad to connect outlying rail ports to the The project was let out to bid early May 2013, and to help support the city’s bid late in May 2013, and awarded shortly there- expanding industrial sector. Due to a high number after, demonstrating the urgency the City had to of accidents involving trains and residents all over get this project under way. American Concrete the city in the late 1800s, the city passed an ordi- Restorations (ACR) was contracted to repair the nance mandating that all rail lines in the city be bridges and retaining walls following the Chicago elevated and, in 1910, the Bloomingdale Line was Department of Transportation Structural Repair of raised to 15 ft (4.6 m) above street level. Concrete Specification, which gives the contractor Use of the line greatly reduced in the 1980s a choice of formed concrete repair or shotcrete. and train service was eventually rerouted to other Due to the need for extensive coordination with rail lines. By the mid-1990s, all rail activity the surrounding communities, ACR was finally ceased, creating an ideal platform for an elevated called upon to begin work in late October 2013. rails-to-trails conversion. The out-of-service rail With frost already present and frigid cold line was largely left alone and reclaimed by temperatures soon to be upon Chicagoland, ACR wildlife and plants. The idea for “The 606” has devised a plan to keep the project moving forward its origins in the CitySpace Plan of 1998, which through the winter months. This plan consisted showed the Logan Square community area did of performing the necessary concrete removals at not meet minimum standards for open space per the bridge locations followed by fully enclosing capita. In fact, of the 77 community areas, it and heating the structures for shotcrete work to ranked second to last at 99 acres (40 ha) deficient proceed. Along with a late start in the year and for the population. In 2004, the City of Chicago the cold weather setting in quickly, this project adopted the Logan Square Open Space Plan, had a variety of obstacles, including access into which helped identify ways to increase open heavily congested neighborhoods and residents’ space to achieve the minimum standards. The properties, repairs during limited closures of main Bloomingdale Line was called out as a way to thoroughfares, and a structure that was in much provide open space in an otherwise dense and worse shape than originally anticipated (Fig. 1). built-out community. The City of Chicago and the Chicago Park Shotcrete Segment of District, with the support of local residents and The Trust for Public Land, proposed to officially Project Overview repurpose the elevated tracks into a 2.67 mile The shotcrete portion of “The 606” was located (4.29 km) long recreational trail for biking, run- at each of the 36 bridges and also the retaining ning, and walking. “The 606” refers to the park walls and caps that spanned the 2.67 miles and trail system that is currently under construc- (4.29 km) of the project on the north and south tion, the centerpiece of which is the Bloomingdale sides of the trail. Work at the bridge locations

30 Shotcrete • Winter 2015 encompassed the entire substructure including the wing walls, abutments, columns, and parapets. Each of the 36 bridges crossed two-lane streets, had three piers, and 15 columns. The trail also crossed five arterial streets, each with four lanes of traffic. At these locations there were four piers and 20 columns. At the longest bridge crossing, Humboldt Park Boulevard, it crossed six lanes of traffic, and there were 11 piers and 33 columns (Fig. 2).

Challenges Upon commencement of the project, ACR realized that the bridges were in far worse condi- tion than shown on the plans. Quantities imme- diately began increasing, as did the depths of the repairs, due to the fact that these walls were Fig. 1: Repair areas were found to be not only much larger in the field but constructed with 1 in. (25 mm) unwashed river also deeper than was called out on the plans and also lacking any rock aggregate and without reinforcing steel. It reinforcing bar was imperative to maintain excellent communica- tion with the general contractor and the owner’s engineers to verify work to be done and any additional repair steps to be taken, such as the addition of reinforcing bar, shoring, and identi- fying areas of complete deterioration requiring full replacement. Because all the bridges are in close proximity to residences, schools, daycare centers, parks, dog parks, small businesses, and main thorough- fares, some special precautions had to be taken to protect private property and also to protect the heavy pedestrian and motor traffic that trav- elled through these areas. Along this 2.67 mile (4.29 km) jobsite, ACR encountered numerous neighborhoods encompassing various demo- graphics. Many work zones were located adjacent to schools, requiring ACR to use extreme caution when conducting repairs and moving machinery in close proximity to young children who are Fig. 2: Repaired 11 piers spanning 250 ft (76.2 m) over six lanes of traffic often unaware of their surroundings and the dangers of a construction zone. Due to the congestion of the work area and the proximity to neighboring homes, parks, and schools, ACR sandblasted with water to keep dust to a minimum. ACR also cleaned up their work area at the end of every day to prework conditions, thus leaving the neighborhood safe for pedestrians and vehicle traffic (Fig. 3). As the bridges provided the only means of travel for residents from one side of the trail to the other, ACR had to phase its work at the bridge locations, keeping one lane of traffic and one sidewalk open at all times. ACR encountered both winter and summer conditions during the course of the project. This change in environment called for different approaches to quality control. When starting the project in late October, the cold temperatures of the infamous 2013-2014 Chicago winter were Fig. 3: ACI Certified Nozzleman shotcreting newly-reinforced repair areas

Shotcrete • Winter 2015 31 already setting in. ACR devised a comprehensive thermometers to confirm the temperature of the plan for dealing with the upcoming winter months substrate, water, pre-bagged material, and mixed to accommodate low temperatures of up to –40°F material stayed at or above the specified minimum (–40°C) wind chill temperatures. Each bridge was temperatures. The temperatures were recorded on wholly enclosed using heavy-duty, fire-retardant quality control checklists every hour to document tarps (Fig. 4 through 6). ACR also deployed large ACR’s ability to maintain a high-quality shotcrete propane heaters to ensure proper ambient and mixture. ACR’s plan succeeded in providing substrate temperatures. Where full road closures quality repairs while allowing the project to were necessary, ACR was allowed a maximum progress through the brutal Chicago winter. of 2 weeks to complete the work on the specific Upon the arrival of the hot summer months, bridge, including 7 days for curing, to satisfy the ACR had to pay special attention to make sure restrictions of the City of Chicago permits for the shotcrete mixture remained at satisfactory street closures. ACR also used heaters to keep the maximum temperatures. To maintain the tem- water warm for mixing and torpedo heaters to peratures required in the specifications, ACR warm the skids of pre-bagged material and the replaced the water supply midday with fresh cold staging area. ACR used both infrared and standard water or added ice to the water supply containers. When possible, ACR’s staging area along with the pre-bagged skids of material were set on the North side of the bridge next to the retaining wall to decrease the amount and duration of direct sun exposure. If this was not possible, canopies erected over the material and shotcrete pump provided shade to aid in temperature control. Similar to the winter months, ACR used infrared and standard thermometers to verify the tem- perature of the substrate, water, pre-bagged mate- rial, and mixed material to ensure they stayed below the specified maximum temperatures. The

Fig. 4: Heated enclosures were installed on portions of bridge during winter months

Fig. 5: Large propane heaters kept temperatures inside enclosure within Fig. 6: Shotcrete placement inside a heated specifications during cold winter months bridge enclosure

32 Shotcrete • Winter 2015 temperatures were also recorded on quality con- trol checklists every hour. The retaining walls posed an entirely differ­­­­­­- ent set of challenges. The walls ran the entire 2.67 miles (4.29 km) length of the trail between the bridges on both sides of the trail. Many of these walls were located in the backyards of residents and some of the houses were very close to the walls, at times separated only by a 4 to 5 ft (1.22 to 1.5 m) pathway. ACR had to coordinate with the general contractor and owner’s engineers on a daily basis to ensure that the residents permitted ACR adequate access to their yards to perform the work. In addition, some of these homes maintained elaborate gardens and expensive landscaping, requiring specialized property protection. Specifically, one of the yards ACR needed to access housed a picturesque koi pond and an herb garden owned by a well-known chef. This garden is closely tended by a professional gardener, and the harvest is used in several restaurants (Fig. 7). Thus, ACR had to deploy multiple levels of pro- tection for the plants and planters from dust, debris, and overspray. Further, the retaining wall next to this garden was covered in decorative vines, and ACR had to coordinate with the chef’s gardener to ensure proper pruning or removal without unnecessary damage to the surrounding foliage. In other areas, ACR had to install tempo- rary framing on the outer edge coupled with protective mesh and tarps to ensure that the shotcrete work was not damaging homes and yards. ACR also encountered an area of retaining wall where the cap was directly above a residen- tial balcony. To perform removals and shotcrete repairs without damaging property below, two stages of protection were deployed. First, ACR installed a fabric tarp along the guardrail of the trail to keep debris from travelling over the side. Additionally, the area designated for repair was framed to ensure that all chipping debris would remain on the trail-side instead of falling to the balcony and property below. This one-sided formwork also gave the nozzleman something to shoot against. As ACR progressed along this 2.67 mile (4.29 km) jobsite, encountering different temperaments of residents, gaining permission to access the repair areas along the retaining walls ran the spectrum of difficulty.

Significance to Project When compared to form-and-place repair techniques, shotcrete proved a far more efficient method of repair on the 36 bridges and miles of retaining walls that allowed for quicker comple- tion with excellent structural capability. As in all construction projects, time was of the essence. Fig. 7: Elaborate gardens of homeowners Many of the bridges required the erection of required covered repair areas that needed shoring towers simply to stabilize a severely thorough planning, preparation, and coordination

Shotcrete • Winter 2015 33 deteriorated substructure and required them to be requirements. All of the compressive strength test in place until the specified 14-day compressive results exceeded the specification’s requirement strength tests of the shotcrete was met. The use and the shotcrete solution resulted in a long-term, of shotcrete and its versatility had many advan- affordable repair with minimum impact on the tages over form-and-place. One advantage was surrounding community. the ability to remove the shoring towers long before the 14-day compressive strength require- ment when the pre-bagged shotcrete material Kevin Doyle graduated from reached 70% of its strength. This allowed for The Ohio State University in reopening the streets in compliance with the City 2009 with a bachelor’s degree of Chicago’s permit requirements. Another advan- in construction management. tage in using shotcrete was repairing the retaining Having worked for a privately walls adjacent to private backyards, including that owned government contractor of a well-known chef. ACR staged the shotcrete out of college, Doyle gained the equipment on the opposite side of the trail and experience from the owner’s ran the shotcrete hoses up and over the trail as perspective that would prove valuable once he opposed to through the yard and gardens. In addi- joined American Concrete Restorations, Inc., in tion, this set-up eliminated the need for tradesmen April 2013. Doyle brought his understanding of to access the yards to set-up and strip formwork the necessity for strong communication and team- for a form-and-place operation, thus completely work between a contractor and owner to this preventing the damage or inconvenience that project and helped to ensure project progress access could create. Using the shotcrete method remained on track. “The 606”-Bloomingdale also meant that there was no possibility of a form Trail is his first major project in which he helped blowing out during casting and damaging the manage, and thus Doyle is extremely proud that yard. The shotcrete process also allows a visual it has been awarded ASA’s 2014 Outstanding confirmation of encapsulation of the reinforcing Repair and Rehabilitation Project. bar throughout the shotcrete placement process, while cast-in-place work requires casting into a closed form where incomplete consolidation and The Outstanding Repair resulting voids aren’t evident until stripping the & Rehabilitation Project forms. After the shotcrete was placed, a double layer of curing compound was applied, thus Project Name 606-Bloomingdale Trail | Viaduct Repairs eliminating the need to impede on private prop- erty for any form removal, grinding, or patching. Project Location The scope of work resulted in over 15,000 ft3 Chicago, IL 3 (425 m ) of removal and replacement with high- Shotcrete Contractor quality shotcrete. All the shotcrete was placed by American Concrete Restorations, Inc.* ACI-certified Nozzlemen employed by a qualified shotcrete contractor. The shotcrete was placed General Contractor with a 0.42 water-cementitious materials ratio, Walsh Construction along with the addition of 10% by weight of Architect/Engineer 3/8 in. (10 mm) river rock. Safety, time, and Transystems quality all significantly contributed to the very Material Supplier/Manufacturer successful use of shotcrete by the Chicago Depart- SPEC MIX*, Putzmeister Shotcrete Technology* ment of Transportation (CDOT) on “The 606” project. The general contractor and the subcon- Project Owner tractor are also proud of their safety record of zero City of Chicago—Department of Transportation accident reports while working in one of the most *Corporate Member of the congested parts of the city. All work was done to American Shotcrete Association OSHA regulations and CDOT environmental

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